Section 11.  Programming Resource Library 
122 
Scalar mean horizontal wind speed, S: 
 
where in the case of orthogonal sensors: 
 
Unit vector mean wind direction, 
 
where 
 
 
or, in the case of orthogonal sensors 
 
 
where 
 
Standard deviation of wind direction (Yamartino algorithm) 
 
where, 
 
and Ux and Uy are as defined above.